1. Field of the Invention
The invention relates to a frontal (axial) magnetic coupling provided with at least one magnet for the transfer of torques or forces from a first enclosure to a second enclosure wherein the enclosures are separated by an isolating wall.
2. Description of the Prior Art
A separation of enclosures is necessary when energy (or information) is to be transferred from a first enclosure having specific climatic conditions, into a second enclosure, by mechanical means in response to torques or forces and turning angles or displacements. Climatic conditions prevail in the second enclosure which are different from and incompatible with those present in the first enclosure. Such incompatibility of differing enclosure climatic conditions often arises in procedures involving enclosures of gaseous or liquid media especially if the media are also corrosive, aggressive, poisonous, explosive or radioactive, or if extreme requirements of cleanliness are to apply.
An application involving corrosion may, for example, occur in the case of medication dispensing equipment. Here, extreme requirements relative to dependability and durability are applied. This is of even greater importance in the case of medication dispensing devices which are to be implanted in the body of a patient. Because of the moisture associated with a fluid or gel-like medication, sensitive components, e.g., a motor, electrical contacts or a battery may be functionally impaired or its power output undesirably effected.
In order to remedy this situation, it is useful to divide the medication dispensing device into two regions. This division leads to a dry region in which components to be protected from moisture are located, for example, an electric motor, and a humid region in which those components that come in contact with a liquid medication are located, for example, a pump hose, a medicinal supply reservoir or a pump drive, etc. These two regions are separated from each other by an isolating wall and are hermetically sealed to the outside. The motor and the pump drive are therefore not within the same space, and thus a transmission of forces between the two spaces is necessary. This is made possible by an indirect magnetic coupling which transmits a torque from the first to the second space. One such dispensing arrangement is described in U.S. patent application Ser. No. 658,830 entitled DOSING DEVICE FOR LIQUID, filed in the name of Franetzki, et al., (corresponding to German Publication No. 33 38 002), assigned, like the present application, to Siemens AG and incorporated herein by reference.
It has been shown that because of the attraction due to axial forces of the two parts of a frontal magnetic coupling, a costly bearing construction is necessary in order to insure a definite spacing of the rotating magnets from the dividing wall. Moreover, the force required for the pump drive is often considerably higher, due to friction, than the case where the axial forces are compensated for. Although magnetic means for the relief of bearing loading are known in the technology; they are, however, of limited application in miniaturized equipment, for example in medication dispensing equipment, since they take up substantial space. Such known means for relieving bearing loading are particularly inapplicable to implantable medication dispensing equipment where millimeters must be dealt with in individual components of construction.